Hi, Sergey! I meditated about it for some time. I remember i was thinking on that part before and did that so for some reason. Though either i was wrong or didn't finish what i planned. This time i'd say we should allow numeric constants there too. Here's the patch i'd push to fix this: https://github.com/MariaDB/server/commit/9c518e4cc9b0569cae2daa5a4024e209293eca45
Best regards. HF On Wed, May 26, 2021 at 8:01 PM Sergey Petrunia <ser...@mariadb.com> wrote: > Hi Alexey, > > At the moment MariaDB requires that the values in DEFAULT clauses are > quoted. > Example: > > select * > from > json_table( > '{"intval": 1000}', > '$' columns( > col1 int path '$.intval_' > default '100' on empty > ) > ) as T; > > here, "100" must be quoted, otherwise one gets a parse error. However, the > quoted value is interpreted as an SQL literal. This looks puzzling. > > MySQL-8 also requires that the default value is quoted, but they have a > (very > odd) reason for it: they interpret the default value as JSON: > > https://docs.oracle.com/cd/E17952_01/mysql-8.0-en/json-table-functions.html > says: > > DEFAULT json_string ON EMPTY: the provided json_string is parsed as > JSON, as > long as it is valid, and stored instead of the missing value. Column > type > rules also apply to the default value. > > I am not sure why MySQL chose to do this. Looking into the SQL Standard, > one can > see: > > <JSON table regular column definition> ::= > <column name> <data type> > [ PATH <JSON table column path specification> ] > [ <JSON table column empty behavior> ON EMPTY ] > [ <JSON table column error behavior> ON ERROR ] > > <JSON table column empty behavior> ::= > ERROR > | NULL > | DEFAULT <value expression> > > ... > This doesn't say whether the <value expression> should be interepreted as > JSON > or just as a value. But one can find this passage: > > <quote> > Without Feature T826, “General value expression in ON ERROR or ON EMPTY > clauses”, the <value > expression> contained in <JSON table column empty behavior> or <JSON table > column error behavior> > contained in a <JSON table regular column definition> JTRCD shall be a > <literal> that can be cast to the > data type specified by the <data type> contained in JTRCD without raising > an exception condition > according to the General Rules of Subclause 6.13, “<cast specification>”. > </quote> > > The important part is: > > ... shall be a <literal> that can be cast to the data type specified ... > > which means it is not JSON. It is just a literal, and literal can be a > string > literal (in quotes, 'string') or an integer literal (without quotes) or > other > kind of literal. > > Btw, Oracle Database allows non-string literals in the default clause: > > https://dbfiddle.uk/?rdbms=oracle_18&fiddle=9af7e43ede77ee285e1a65f1f419d3bd > > What are your thoughts on this? > Is MariaDB's behavior intentional? Should we follow the standard and allow > all > kinds of literals? What was the reason for the limitation that default > values > are quoted? > > BR > Sergei > -- > Sergei Petrunia, Software Developer > MariaDB Corporation | Skype: sergefp | Blog: http://petrunia.net > >
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